The fastening of the head to the compressor block and, more precisely, to the cylinder, faces some challenges inherent to the functioning of the compressor. Among these challenges to be overcome are the sealing of the gaskets between the cylinder and the parts that compose the head and also the deformation of the cylinder wall resulting from the transfer of the fastening forces of the head.
Nowadays, the conventional way for fastening the head to the cylinder involves making indexing holes, by which normally four screws pass through that align the set present on the head (valve, valve plates and the head lid) to the holes located around the wall of the cylinder block. An example of this conventional way is illustrated in FIG. 9.
This conventional way presents some drawbacks. Firstly, it is necessary to apply high fastening forces over the screws so that it is possible to guarantee the gaskets sealing, since the contact pressure is more concentrated at the region around the screws, where there is no need to be sealed. These high fastening forces end up generating deformations that are transferred to the cylinder wall. Secondly, there must be holes in all the head components, and mainly threaded holes at the cylinder block, wherein such holes require high precision of position tolerances and high machining time, which, without doubt, significantly raises the cost of such solution.
In relation to the patent documents, the above mentioned way of fastening using screws can be found, for example, in the document U.S. Pat. No. 9,074,591.
Another example can be checked on the document KR 2001054069. Such document describes a solution that uses a clamp to assist the fastening and alignment between the discharge valve, valve plate and suction valve. The clamp is arranged at the front of the head. However, the clamp has only the function of auxiliary the alignment and the fastening, so that the fastening and alignment themselves are still in charge of the same screws mentioned in the conventional solution previously described.
As noted, the state of the art still lacks a head fastening solution for refrigeration compressors that presents low manufacturing complexity and low cost, without further resulting in a decrease of the efficiency of fastening and collateral damage, such as, for example, the increase of deformations on the cylinder wall of the block.